sleep quality and quality-of-life

 

A recent study found that sleep quality was the strongest predictor of sleep-related indicators affecting quality-of-life (see sleep quality assoc with QOL Plos2023 in dropbox, or  https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0282085 )

 

Details:

-- longitudinal data from the Czech Household Panel Study of 4523 respondents in 2155 households, from 2018-2020

-- no information provided on the demographics, comorbidities, or medications taken

-- definitions:

    -- sleep duration: assessing the number of hours of sleep both on free days as well as on workdays, specifically the time respondents usually fell asleep and woke up

    -- sleep quality: a subjective 4-point response to how patients would rate their quality of sleep, from very bad to very good

    -- social jetlag: the mid-sleep time on free days versus workdays (ie sleep changes related to social arrangements on free days that lead to sleeping at times other than for their typical workday times; eg partying… which brings up the related issue of need to control for alcohol and other substances used….)

    -- quality-of-life was assessed by a scale including individual sense of well-being, satisfaction with life, happiness, and meaning in life. assessment of work stress was also part of the questionnaire

 

Results:

Relationship between sleep variables and quality-of-life variables, for both the statistical beta value ("B", the slope of the line) and the statistical p value (NS=non-significant):

 

--sleep duration: 

    -- life satisfaction:

        -- between people: B= -0.02 (-.08 to .03), NS

        -- within the same person: B= -0.01 (-.11 to .09), NS

    -- well-being:

        -- between people: B= -0.01 (-.04 to .02), NS

        -- within the same person: B= 0.03 (-.03 to .08), NS

    -- subjective health:

        -- between people: B= -0.04 (-.07 to -.03), p<0.01 [though the B value is quite small]

        -- within the same person: B= -0.02 (-.07 to .03), NS

    -- work stress:

        -- between people: B= <0.01 (-.02 to .01), NS

        -- within the same person: B= -0.02 (-.05 to .01), NS

    -- happiness:

        -- between people: B= -0.08 (-.14 to -.03), p<0.01

        -- within the same person: B= -0.04 (-.15 to .06), NS

 

-- sleep quality:

    -- life satisfaction:

        -- between people: B= 0.65 (.56 to .74), p<0.001

        -- within the same person: B= 0.15 (.11 to .29), p<0.05

    -- well-being:

        -- between people: B= 0.46 (.42 to .51),  p<0.001

        -- within the same person: B= 0.18 (.10 to .26), p<0.001

    -- subjective health:

        -- between people: B=  0.47 (.42 to .51), p<0.001

        -- within the same person: B= 0.14 (.07 to .21), p<0.001

    -- work stress:

        -- between people: B= -0.04 (-.06 to -.03), p<0.001

        -- within the same person: B= -0.01 (-.04 to .03), NS

    -- happiness:

        -- between people: B= 0.74 (.65  to .84), p<0.001

        -- within the same person: B= 0.28 (.14 to .43), p<0.001

 

--social jetlag:

    -- life satisfaction:

        -- between people: B= -0.09 (-.17 to .00), p<0.05

        -- within the same person: B= 0.11 (-.03  to .24), NS

    -- well-being:

        -- between people: B= -0.02 (-.06 to .02), NS

        -- within the same person: B= 0.03 (-.05 to .11), NS

    -- subjective health:

        -- between people: B= -0.03 (-.07 to .01), NS

        -- within the same person: B= -0.06 (-.01 to .13), NS

    -- work stress:

        -- between people: B= 0.02  (00 to .03), p<0.001

        -- within the same person: B= 0.02 (-.01 to .05), NS

    -- happiness:

        -- between people: B= -0.08 (-.17 to  00), NS

        -- within the same person: B= 0.07 (-.08  to .21), NS

 

-- interpretation: not only was the slope higher for sleep quality and quality-of-life,as opposed to the other sleep parameters, but the relationships were much stronger and more statistically significant

 

Commentary:

-- as has been found in sleep science increasingly, through a variety of mechanisms sufficient sleep is necessary for cerebral restoration and repair, leading to cognitive improvements as well as generally feeling more rested (see http://gmodestmedblogs.blogspot.com/2023/04/stress-decreases-cognitive-function.html , which notes that sleep deprivation is associated with changes in hippocampal function and memory loss)

-- insufficient sleep is also associated with depression, obesity, diabetes/cardiovascular disease, increased risk of cancer, and reduced life expectancy (some of which may be due to the association between sleep loss and inflammation: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548567/ )

-- insufficient sleep quality, as well as sleep quantity and social jet lag, may well be part of the reason that healthcare workers seem unsatisfied and motivated to quit their jobs (see http://gmodestmedblogs.blogspot.com/2023/04/healthcare-worker-burnout-whither.html )

    -- and many healthcare workers have drastically changing schedules (nights for 1-2 weeks, then days for 1-2 weeks) creating much more jetlag (not "social jetlag" but "required jet lag on a regular basis"). and this level of jetlag may actually be a real quality-of-life issue (by the way, i did see a study years ago that it takes 2 weeks for a sleep cycle change to allow for accommodation for the change: ie, those on 2 weeks of days then 2 weeks of nights never actually get into a quality sleep rhythm)

 

--  a summary of prior research:

    -- sleep duration: many studies have suggested that sleep duration is a reliable predictor of well-being, and those with too little or too much sleep seem to have a higher mortality. most studies, however, have found a correlation between sleep quantity and quality-of-life, but there have been a few studies that have not found this to be the case

    -- sleep quality: fewer studies done, many in combination with sleep duration, and most studies targeting sleep quality were in specific groups such as students, patients with existing mental health disorders, and shift workers. The one population study, which was done in Austria, did find that sleep quality was associated with quality-of-life (see https://onlinelibrary.wiley.com/doi/abs/10.1034/j.1600-0404.2000.102004249.x , which used the Pittsburgh Sleep Quality Index of 19 pretty all-encompassing questions relating to sleep (see https://www.med.upenn.edu/cbti/assets/user-content/documents/Pittsburgh%20Sleep%20Quality%20Index%20(PSQI).pdf )

    -- social jet lag: very few and small studies done in students, with inconsistent results

    -- overall, many of the studies were cross-sectional and not longitudinal ones having assessments over time, potentially leading to inaccurate or inconsistent findings

 

--  the major finding in this study was that quality of sleep, as a subjective measurement, is by far the most impressive sleep variable (as compared with sleep quantity and social jetlag) associated with several quality-of-life issues. This was true both on averages of the population studied, as well as for changes within the same person during the course of the study. The only outlier here was work stress which was not related to sleep quality

-- and, the degree of the association between quality of sleep and quality-of-life was not just statistically significant but impressively larger than the association with either the quantity of sleep or social jet lag

-- of note, as found in other studies, there was a negative association (though small) between sleep duration and quality-of-life issues. this could be reverse causation, whereby those with poor quality-of-life (perhaps through concomitant depression or other mental health issues) actually sleep longer

-- The average sleep duration in the Czech Republic is 7.5 hours, similar to other European countries; the reported social jetlag is similarly comparable. The Czech Republic also has a similar standard of living as other European countries in terms of perceived health, life expectancy, and economic activity. So there is argument that the above results are likely to apply to other European countries

  

limitations:

-- there was no information provided about demographics, comorbidities, or medications. this is quite unusual in any study, especially in one assessing sleep, where there is so much relationship between these issues and both sleep quality as well as quality-of-life

-- the evaluation of sleep quality was subjective on a 4-point scale, and individuals may well have very different personal criteria for what they consider adequate sleep quality and how they score it

-- the quantitative assessment of sleep duration is problematic: there might be a sleep latency and the assessment of when sleep actually started is likely not so accurate, there may be short or long time periods of awakening during sleep, and (baseline) people do not seem to quantify actual hours of sleep so well. Anecdotally, I do see many patients with sleep problems stating “I get only 1-2 hours of sleep every night… and do not sleep during the day”, which seems quite improbable……

    -- also, there may have been a strong interaction between these sleep measures and how participants may respond to questions: perhaps those people not sleeping enough hours might well select sleep quality as their sleep problem instead of sleep duration. Perhaps using a more complete sleep inventory (eg Pittsburgh Sleep Quality Index) might produce a more reliable assessment

-- there was a significant drop in sampling participants between 2018 and 2019, felt to be due to blood draw requirements (not part of this study)

-- the study was done in part during the previous bad old days of Covid, which did impose a very different type of life stress. For example, there was a slight improvement in happiness in those who had had poor sleep in the pre-covid data collection. However, there were many other variables in play during Covid lockdown, including changes related to work stress, social interactions, having more relaxing time at home etc: these all may have affected happiness, differentially for different people

-- though this was the first longitudinal study of sleep and quality-of-life, allowing for within-person assessments over time, the total time of the study was still short and was distorted some by the emergence of Covid

-- the average duration of sleep was only 7.5 hours; there was a strong argument in the very informative book  “Why We Sleep” by Matthew Walker that this number should be closer to 8.5 hours…. (this is a really good read, and one that does not put you to sleep)

-- this study was observational and evaluated associations, so the results cannot be interpreted as causal

 

so, this study does add significantly to the sleep literature: sleep quality seems to be the single most important sleep parameter in terms of quality-of-life, far outweighing sleep duration or social jetlag.  it would be useful to know if there were other health effects, such as cognitive functioning, or perhaps other associations with sleep deprivation, such as hypertension or diabetes (or glucose control in patients with diabetes).

 

the study  also brings up a common clinical scenario of patients having trouble sleeping. the nonpharmacologic approach through sleep hygiene is reasonable, though the data finding benefit are not so great. so, people often end up on drugs, including many OTC (eg diphenhydramine).  But these medications do affect sleep architecture as well as sleep apnea and periodic limb movements, both of which affect sleep (see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8848521/ ): some (eg lithium, trazodone, and some antipsychotics) do increase slow-wave sleep, which seems to be related to feeling rested the next day. some very old studies did suggest that trazodone had less effect on sleep architecture than other meds. But it would very helpful to have comparative research on the different specific meds, polysomonography, and patient assessments of sleep quality....

 

 

geoff

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